I remember reading in some business magazine from the 70s, perhaps financial times about the Shah of Iran's investments in US companies. It mentioned his financial stakes in all sorts of US corporations including Pan Am. Supposedely he wanted to purchase a large share of the airline but wasn't allowed to.

Concerning foreign ownership in US airlines:
"Airlines still have to be substancially owned and effectively controlled by their own nationals even though minority ownership by foreign ownership by foreign individuals or companies may be permitted. In the United States the position is still that only up to 25 per cent of foreign ownership of its airlines may be allowed, despite the recommendation of the National Commission to go to 49%."
Taken from:
The airline business in the twenty first century